1. Field of the Invention
The present invention relates to a vapor cooled semiconductor device which cools a semiconductor element by utilizing the latent heat of vaporization of a liquid coolant.
2. Description of the Prior Art
As is known, the conventional vapor cooled semiconductor device comprises a liquid coolant which is enclosed in a closed envelope or container with given open space, whereby heat generated from a semiconductor dipped into the liquid coolant is radiated to an outer part by repeating vaporization and liquefication of the liquid coolant. The thermal conductivity in such cases is quite high, compared to those of air, oil, water, and the like, whereby the cooling efficiency to the semiconductor element is advantageously remarkably high.
In spite of the advantages for cooling the semiconductor element, however, the following disadvantages of the conventional devices have been found from the structural view point.
That is, in the conventional device, the semiconductor element is assembled in a stack comprising a metallic electrode, a radiator, an insulator, a pressing mechanism of a pressure plate and clamping bolts. The stack containing the semiconductor element is enclosed in the closed envelope. Accordingly, the number of parts of the device are large, the structure is complicated and the steps of manufacture are many and detailed. Further, the required pressure for the device increases, depending upon the increase of rating volume of the semiconductor element, and, accordingly, the size of the stack and the size of the closed envelope enclosing the stack are increased because of the mechanical strength required for the pressing mechanism to be durable to the high pressures being generated. Of course, the amount of the liquid coolant enclosed in the closed envelope is increased.
As a result, the size of the whole device is increased and the weight of the device is also increased, and accordingly, the cost of the device is significant.
Moreover, in the conventional device, the whole part of the stack is enclosed in the closed envelope, whereby a terminal of the semiconductor element for current should be led out by an insulated and closed terminal disposed on the wall of the envelope, being insulated from the envelope. Therefore, the size of the device is further increased and the structure of the device is thus more complicated.